Temperature relationships of fungi isolated at low temperatures from soils and other substrates

Abstract

A study of the temperature relationships of 20 mycelial and yeast fungi which had been isolated at low temperatures from soils and from abattoirs indicated that few fungi can be regarded as truly psychrophilic. Only 1 species failed to grow at 25C. Although all the species investigated were able to grow at 4C and can therefore be considered as potential spoilage organisms on refrigerated foods, their optimal growth temperature was either 15C or 25C. The 20 species could be divided into 4 groups in relation to their temperature relationships, particularly their optimal temperatures and their ability to grow at 30C.

A number of fungi able to grow at 4C has been isolated from soils and from abattoirs in New Zealand (1, 2). Several mycelial fungi can show reasonable growth below 10C, and some even down to −10C, but, when laboratory studies have been performed, most of these fungi prove to have an optimal growth temperature at 25C or above (3). These fungi, however, can be a cause of serious spoilage of a variety of refrigerated foods and even at the temperature currently used for meat storage ( −12C), occasional consignments of meat are encountered which show the characteristic spots of fungal contamination. During investigations into the occurrence of these fungi in an abattoir, (1), 9 mould and 4 yeast species were isolated which could grow at 4C, and further studies into the reservoirs of these fungi in the outside environment resulted in the isolation of a further 8 mould and 2 yeast species (2). This paper reports on investigations into the temperature relationships of 20 of these species.